The present invention relates to a method of employing a device embodying a cannula so as to insure the cannula's destruction and safe storage after use. The method is especially useful for needles that have come into contact with human blood and which are adapted to be used only once.
Cannulas and equipment used for sampling blood and injecting therapeutic fluids frequently are disposable and designed to be discarded after a single use. Once a cannula has been used to draw blood or inject a medication, it is contaminated. The sharp point on a contaminated needle can injure people and cause the spread of disease among those that handle it. Infectious diseases such as HIV or hepatitis viruses have been transmitted to people who handle contaminated needles and accidentally stick themselves with them. Small residues of blood and viruses on the cannula from an infected patient can result in transmission of a disease that the patient has contracted to a staff member.
In the past, relatively complex arrangements have been devised to prevent the accidental infections from contaminated needles. I have found that destruction of the cannula and covering its sharp point(s) is highly desirable because hypodermic needles are frequently reused by drug abusers and accidental contact or intentional use must be eliminated.
Exemplary of devices which have attempted to solve these problems is the application of Ameur: Int. Pub. No. W089/11304; PTC/SE89/00290. The application discloses a pair of protective sleeves that are displaceable in a longitudinal direction over a holder that is provided for a double pointed cannula. The sleeves serve as adapters that provide a bayonet socket which is fitted into another bayonet socket. The arrangement is used with a sample holder which has steps formed in an end to receive a peg that holds the arrangement together during use. As viewed, the sleeves of the cannula can easily move and expose the needle after use when it is contaminated. Moreover, the arrangement requires the provision for a specially designed sample holding device to accommodate the sleeves and even with this fairly complex combination, the needle is not destroyed after use.
In the United States Patent to Wardlaw, U.S. Pat. No. 4,366,544, patentee describes a hypodermic syringe which has provision for preventing more than one use and rendering the needle inoperative. According to the Wardlaw patent, a mechanism is mounted on the syringe which, after administering the injection, is manipulated to bend the needle of the syringe at a right angle and concurrently retract it from its normally projecting position to a second position in which it is housed in a cavity. The retraction is accomplished by twisting a cap around a post so that the needle is permanently deformed and wrapped around the post. while protection of the needle point and destruction of the needle is provided with the mechanism, significant torque is required to twist the cap to urge the needle around the post to destroy and house it. The amount of torque necessary to accomplish the wrapping and housing can exceed the strength of the various plastic parts.
Capping arrangements such as shown in Lemelson, U.S. Pat. No. 4,273,123; Karmen et al, U.S. Pat. No. 3,747,812; and Cuu, U.S. Pat. No. 4,634,428, all involve an ancillary cap over the cannula to bend or distort the metal. Similarly, the U.S. patent to Koening, U.S. Pat. No. 3,893,608, discloses a syringe that is fitted onto a cover to distort it through the placement of a post surrounding by an annular ring.